An M/G/1 queue with an optional second vacation

This paper deals with an M/G/1 queueing system with an additional phase of second vacation, where after first phase of regular vacation the server may take an optional second vacation. In this paper we first derive the queue size distributions at a random epoch and at a departure epoch. Next we obtain the Laplace Stieltjes tranform of waiting time distribution. Also we obtain some important system performance measures of this model. Finally, we present a transformation free method to obtain the mean unfinished work.